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北祁连中段俯冲—增生杂岩/火山弧的时代探讨
A Tentative Discussion on the Ages of the Subduction-Accretionary Complex/Volcanic Arcs in the Middle Sector of North Qilian Mountain
  
中文关键词:俯冲-增生杂岩 火山弧 HP/LT变质作用
英文关键词:subduction accretionary complex  volcanic arc  HP/LT metamorphism
基金项目:国家自然科学基金资助项目(49172128)
作者单位
张建新  
许志琴  
陈 文  
徐惠芬  
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中文摘要:
       北祁连中段俯冲-增生杂岩/火山弧由俯冲-增生杂岩和火山弧两个单元所组成,前者以早奥陶世具洋壳性质的蛇绿岩、蛇绿混杂岩及深海复理石为主体,夹中、晚寒武世大陆裂谷及洋陆过渡环境的火山岩及碎屑岩块。同位素年代学显示俯冲-增生杂岩的深部单元经历了489—440Ma的HP/LT变质作用,而火山弧的形成时代为495—466Ma,它们均形成于O1—O2期间早古生代祁连洋向北俯冲在阿拉善地块之下的俯冲作用。
英文摘要:
       The subduction-accretionary complex/volcanic arcs in the middle sector of North Qilian may be subdivided into subduction-accretionary complex zone and the volcanic arc zone. The former mainly comprises the Early Ordovician ophiolites, ophiolitic melanges and deep-marine flysch with features of ocean crust, within which the Middle to Late Cambrian volcanic rocks and clastic rocks characterized by continental rifting and continent-ocean transitional environment occur as lenticular blocks.Isotopic data show that the deep unit of the subduction-accretionary complex experiencedHP/LTmetamorphism during the period of 489—450Ma and the age of volcanic arcs is 495—466Ma, and that these geological bodies were formed as a result of northward subduction of Paleozoic Qilian oceanic crust beneath the Alxa blocks during the Early to Middle Ordovician.
张建新,许志琴,陈 文,徐惠芬,1997,北祁连中段俯冲—增生杂岩/火山弧的时代探讨[J].岩石矿物学杂志,16(2):112~119.
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